Welding Synchro Cones---is it needed?

[Bruce2]

For decades everyone has been welding the synchro cones to the gears, because you have to. Or do you?
What do you think about synchro cones pressed on with Loctite for cylindrical part bonding? Anybody relying on Loctite?

[PEPPE]

i used both systems. my faster friends have welded ones. i prefer loctite because it is easier to remove and service. no loosing happened to me, but i've never applied extreme torques.

[Pablo2]

Ages ago, we tried to retain splined synchro cones with Loctite. It didn't work. So, if the bond isn't even strong enough to keep splined cones from pulling off, I doubt that it's strong enough to keep plain cones from spinning.

[Bruce2]

The stock press fit does pretty well with stock engines. My guess is that with properly applied Loctite 680 (Cylindrical part bonding), the cones should be able to transmit more torque than stock. Agreed?
Any guesses how much more?

[Dougy Dee]

Looking at the Henkel NA site

http://www.henkelna.com/about-henkel/pr ... =technical

indicates that "for metal parts Loose Fitting/Slip Fit".

I suppose a test rig could easily be set up to get an indication of how much torque is required to spin or break free a stock press fit and chemically enhanced gear set... Shock loads could also be induced ...

[Bruce2]

Check my math.
The dia is 49mm (1.93") and length is 14mm (.551")
Given the performance in Dougy's link (4000 psi), my math says it will take just over 1000 ftlbs to break the bond.
I don't think shock loads are that important since we're only dealing with 3rd and 4th. 1st gear would be different.

I might just glue together one then put it in my press to see if 12T can break it apart.

[Piledriver]

The green "permanent" stuff for rod bushings etc is pretty stout.

[Pablo2]

"for metal parts Loose Fitting/Slip Fit".

My impression of these products has always been "of some use in 3rd world emergency situations" (like broken down in Kenya), but in no way a substitute for properly fitting VW or Porsche transmission components. Like I said, it couldn't even keep the dog teeth from pulling off a snug-fitting splined gear, which in my way of thinking was asking FAR less of the product than what is suggested in this thread. (Splined-on dog teeth offer far more opportunity for a retaining goo to perform than press-fit teeth.)

Now, if you were to use a dremel to form just a few intersecting spiral grooves on both the gear's OD and the cone's ID, in which the hardened crystals had some purchase, the chance of success might be higher.

[raygreenwood]

The stock press fit does pretty well with stock engines. My guess is that with properly applied Loctite 680 (Cylindrical part bonding), the cones should be able to transmit more torque than stock. Agreed?
Any guesses how much more?

Bruce2......is that what they man by the term "cylindrical part bonding".....an adhesive joint? I have no idea....but I always figured that term was used for "spin welded/friction welded parts".
I would think that could do really well for bonding these components if alignment could be maintained. Ray

[Bruce2]

It's like gluing two cylindrical parts together, Ray.

I did some tests. The first test was to bond them in exactly the condition the parts were made. Cleaned them well with Brake Kleen, then pressed them together with Loctite 680 spread evenly over both parts. Directions stated 24hr cure at room temp. I gave it a few more days. The reading I got when I pressed it apart converted to 400 ftlbs.

Next was to rough up the surfaces with some 60 grit sandpaper. I made sure not to lean on the parts to affect the press fit. Also note that every time you press the parts on and off, it wears out the press fit, so any reduction in grip could be due to that. However, this time it took more force to push the parts apart. Converted, I get 530 ftlbs. The sandpaper definitely helped.

Comments?

[raygreenwood]

It's like gluing two cylindrical parts together, Ray.

I did some tests. The first test was to bond them in exactly the condition the parts were made. Cleaned them well with Brake Kleen, then pressed them together with Loctite 680 spread evenly over both parts. Directions stated 24hr cure at room temp. I gave it a few more days. The reading I got when I pressed it apart converted to 400 ftlbs.

Next was to rough up the surfaces with some 60 grit sandpaper. I made sure not to lean on the parts to affect the press fit. Also note that every time you press the parts on and off, it wears out the press fit, so any reduction in grip could be due to that. However, this time it took more force to push the parts apart. Converted, I get 530 ftlbs. The sandpaper definitely helped.

Comments?

Nice info! Thanks.
Yes, thats the problem with interference and press fits. The surface fatigues and each successive press fit is a little different.
So it sounds to me like what you are doing with this system is to carefully impart some 3-dimensional texture to the surface of each part. The adhesive fills the voids in each surface...linking the voids across the gap. If the part tries to move....the adhesive accts more like a wheel chock to keep movement from starting.

It makes an enhanced press fit. Interesting. Ray

[shepherd]

Can any of you point me to a picture showing how you set up the gear/ hub assembly to separate them? I'm pretty far into my first transmission rebuild, and this has got me stumped. The gear and hub diameters are so close that there isn't a step to use, and the space between them so little that I don't see how a bearing splitter can work without causing damage. I've purchased loctite green sleeve retainer for the reassembly, any help getting it apart will be a huge help!
SD

[Marc]

Up to ~130 lb-ft => Loctite should suffice. Beyond that, IMO it's foolish to try to get away without welding. Might handle 150, but it's anyone's guess as to how long.

[Casting Timmy]

Wanted to add some to this topic, I have been using Loctite for less than a 150 ftlb of torque motors to maintain serviceability on boxes that don't need tons of strength. I've also read recently that welded gears honed back out still can warp the cone surface and lead to noisy gears (Scott said something to this affect on thesamba). So an added benefit to Loctite or stock set ups is they're stock and will act like it. Anyone have experience with welded gears whining?

On higher torque builds I go for welding that doesn't require rehoning the gear as I don't think that much heat is needed in the gear. Another Scott thread I saw he popped the "welded" gear set apart in the press, can lighter forms of welding give more strength and allow some serviceability with possibly still being broken apart on the press?

Conversing with Pablo2 on splined hub gears, I would agree they don't seem to adjust out the same as stock. I keep wondering if they could be TIGged in a couple spots to keep the hubs from floating.....but my gut thought is the hubs are too loose and going on and off power would be solely carried on the welds and not the splines. It is a great system from serviceability, but it would be interesting to drive one as I just know what I felt on the jig and talking to Pablo2.

[Bruce2]

I've also read recently that welded gears honed back out still can warp the cone surface and lead to noisy gears ....... Anyone have experience with welded gears whining?

Problems with fit or warping depend on the welding techniques used. One welder may put a ton of heat into the parts and warp them, while the next guy knows how to minimize the heat in the parts. Also, the mass of the gear is a big factor. Warpage of 3rd is more likely than 4th.
I've never noticed a correlation between welding and noise in gears.

.... he popped the "welded" gear set apart in the press,

If you're able to press apart a welded gear, then you didn't get enough penetration in the weld. I wouldn't view being able to press them apart as being a benefit.

If you had a properly welded gear and you need to change the synchro cone, just bore out the synchro cone to shorten the gear, cutting away the weld.